In-head Wedge Grips (Vee)

Designed as an integral part of the testing platform, vee wedge jaws fit directly into the crosshead pocket of the frame and provide a grip that is adaptable to a variety of testing applications. These jaws are rugged heat treated steel and ideal for testing a variety of round specimens. Most of the offered vee wedge jaws can also be produced using through-hardened tool steel, which is suitable for re-bar applications.

The teeth of the jaws are also hardened, and different tooth options increase the application range: a coarse tooth pattern is best for softer materials and higher loads, whereas a finer tooth pattern is best for harder materials.

The wedge design causes the gripping force to increase as tension force is applied. This ensures a secure gripping action, which decreases occurrences of slippage throughout the range of the test.

Filler plates are provided with the purchase of testing frames and allow a variety of specimen thicknesses to be tested. The filler plates adjust the opening of wedge jaws by changing the width of the crosshead pocket. All plates should be used for the thinnest specimens and no filler should be used for the thickest specimens.

The variety of available jaws also allows variability in the range of specimen diameters. This versatility is due to the different depths and angles of the vee notch in the jaws available, depending on the specific dimensions of the specimen being tested.

Principle Of Operation

A pair of wedge grip jaws is used in each crosshead pocket to grip the upper and lower end of the specimen. The grip jaw pairs are actuated (opened and closed) by one of two basic methods: pinion or lever arm. The method used depends on frame model and frame options purchased.

When pinion actuation is used, the back surface of each grip jaw is equipped with rack teeth to facilitate actuation of the jaws in the crosshead pocket. A pinion meshes with these rack teeth and as the pinion is actuated by the operator, either manually or hydraulically (depending on frame options), the jaws are raised or lowered in the crosshead pocket.

When lever arm actuation is used, a grip hanger is attached to each grip jaw with two bolts.

Once the jaws are installed in the grip pocket, the grip hangers will pivot about a lever arm. As the operator actuates the lever arm, either manually or hydraulically (depending on frame options), the jaws are raised or lowered in the crosshead pocket.
Once the specimen has been inserted between the jaws, the operator applies an initial clamping force to the specimen with the pinion or lever actuators (depending on frame options). When the test is begun, the wedge design of the grip jaws and pocket translates some of the tension force applied by the load frame into a gripping force on the specimen. As the tension force increases so does the gripping force, this reduces instances of specimen slippage.

Application Range

Jaws are rated to full machine capacity - up to 3000 KN (600,000 lbf; 300,000 kgf)

Designed for testing specimens in compliance with ASTM E8 standards

Wedge design causes gripping force to increase as more tension force is applied

Filler plates allow the user to test a range of specimen thicknesses with the same set of jaws

Operate in static tension only

Suitable for use with a variety of round specimens (including pipe, bar, tube and re-bar) made of a variety of materials (including steel, wrought iron, copper, bronze, brass, aluminum, and composites)